I have worked with a lot of different forming systems for different roofs, The largest to date is approx, 6M X 6M. Small roofs can be supported from above, but larger roofs are easiest with some center support. Since the roofs are self-supporting and poured slowly, very little reinforcing is necessary. Once a lower form mold is made-up (typically pieces of 3/8 re-bar), it can be easily moved in sections to form an identical roof. That makes this system ideal for hotel roofs, where the roofs are usually small, and 2 or 3 basic roof designs can be used for the entire job. Steps: Lower the formwork from a poured roof and move to the next unit, then pour the thin, initial shell. The next day, pour the roof. Since the roofs are self -supporting, you can move the form again in 3 or 4 days to the next unit. These roofs could be quite sculptural and interesting, (i.e. shells).